1. Field of the Invention
This invention relates to a method for growing plants and an apparatus for growing plants for hydroponic vegetables, flowers, grasses, and so forth using an artificial light source.
Furthermore, this invention relates to an improved cultivation apparatus and an improved cultivation method for growing plants very efficiently, in which a cultivation room is covered with a reflection layer, a fluorescent light is used as the artificial light source, and a pump forcibly blows air containing high density carbon dioxide gas into cultivation water solution in a cultivation container.
2. Description of Related Art
The several kinds of hydroponic cultivation apparatuses and methods for growing plants without using sunbeams and natural soil have been well-known.
The apparatuses, for example, have been found in an official gazette for Toku-Kai-Hei 7-50941, Toku-Kai-Hei 7-50929, Toku-Kou-Hei 6-61190, Toku-Kai-Sho 63-240731 developed by the present inventor, and Toku-Kai-Sho 62-55028.about.55029.
The above-described conventional embodiments are the apparatuses in which a fluorescent light is used as a light source of the hydroponic cultivation, the position of the fluorescent light is moved along with the growth of the plants, the distance between the upper portion of the plant and the position of the fluorescent light has been kept constant within the predetermined length.
However, in the hydroponic cultivation, especially for green vegetables, it has been a problem to cause a heat trouble. The heat trouble is a phenomenon in which a leaf is crinkled up and/or becomes black (chip-burn). It is very important that strong attention should be paid in order not to cause the chip-burn in the hydroponic cultivation because the commercial worth of the cultivation green vegetables becomes nothing if the part of the leaf, to say nothing of the whole leaf, has caused the chip-burn.
The hydroponic cultivation using an artificial light source, such as a high pressure sodium light or a metal halide light, producing a lot of heat energy usually causes the heat problem. Accordingly, the distance between the leaf and the light should be adjusted in order to avoid this kind of problem.
It has been considered that the chip-burn has been a phenomenon in which the surface of the leaf has been damaged because the heat energy of the artificial light source has been stored in the leaf surface and the radiation of the stored heat energy has not been done fully. The natural sunbeams would not cause the chip-burn, but the artificial light cultivation would cause the chip-burn.
Therefore, the chip-burn will be avoided if the heat radiation from the leaf surface will be made fully and the heat generation (especially radiant heat) will be made less by performing the high efficiency to contribute the plant growth by the artificial light.
According to the conventional apparatuses, a time (namely, night) has been given to stop irradiation by setting intermittently the irradiation time and/or blowing the cold air on the central portion of the plant. However, there have been defective points such as the complexity of facilities with the increase of the electric power consumption for blowing the cold air and a delay for growing the plants because of not making photosynthesis during the time when the irradiation has been stopped for setting the irradiation time.
There is an idea in which the plants receive the only visible rays through an optical fiber by eliminating heat rays contained in light emitted from the conventional light source (Toku-Kai-Hei 7-107868). However, this idea has not been realistic because a quantity of light has not been sufficient, a large number of optical fibers have been necessary to get a sufficient quantity of light, and the apparatus would be expensive and complex as a result.
Further, it has been considered that a sufficient quantity of oxygen has been necessary for growing a root. Thus, according to the conventional apparatuses, a several centimeters oxygen layer A has been commonly installed between the surface of the cultivation water solution and a cultivation base supporting the plant as seen in FIGS. 4 and 5.
However, these types of apparatuses have not been preferable for growing the plant root because there has been the special portion of the plant root which has been exposed in the air and the plant root rarely grow in the air. It is very important for the plant to grow healthy because the plant should grow healthy and plant leaves' growth is closely related to the plant root condition.
Nevertheless, until now, it has been thought that the plant root has been very easy to decay because of an oxygen supply shortage for the plant root when the whole plant root including the base root has been completely soaked.
Namely, a lot of plant cultivation apparatuses, which have been used for the hydroponic cultivation using the artificial light, have been proposed. FIG. 5 illustrates one example of the above described plant cultivation apparatuses, (a) is a sectioned drawing of a plant cultivation container, and (b) illustrates one example of the plant cultivation base.
In the upper portion of a cultivation container 1, a cultivation base 44, which provides a plurality of holes 43 for accepting the plants, is provided. In the cultivation container 1, cultivation water solution 49 is filled until the water level 45 apart from the plant cultivation base 44. In the case of the same area of the cultivation container 1, the higher water level is preferable as much as possible because the plant roots grow well and cultivation water solution temperature and composition will not change if a quantity of cultivation water solution is large as much as possible. However, it has been necessary to provide space between the water level and the plant cultivation base 44 because cultivation water solution 49 will overflow when a quantity of water is changed and working is made in such a way that the plants are set to the cultivation container 1 or removed from the cultivation container 1 if the water level 45 is extremely high.
However, as described before, if there is space between the plant cultivation base 44 and the water level 45 of the cultivation water solution 49, there is a problem that the roots will not grow well from the root position in the space described above and water wetting the reverse side of the plant cultivation base 44 drops outside the cultivation container from the surface of the plant cultivation base 44, dirties the plant cultivation apparatus, and wets the light source apparatus for irradiating the plants and so forth. Further, water dropping outside the cultivation container may result in the decrease of cultivation water solution quantity of the cultivation container, then water should be added to cultivation water solution to fill up. Further, in the case of multi-layered cultivation structure, when water in the upper cultivation container drops outside the cultivation container, an electric leak will be caused in an electric system of the lower cultivation container.